Tested this several times, and Kamahl’s is not recognizes as a legendary card even though the description states it .
//Edited Title -Brigby
No the spells are not historic : they have the legendary sign to indicate you need a legendary to play it
In paper they are legendary. Also, the description already says you need a legendary out to cast them, they wouldn’t need the icon if they weren’t legendary themselves.
Yes, this seems like a bug.